珊瑚礁工程地质研究进展

珊瑚礁是发育于热带海洋环境中由生物作用和地质作用共同形成的地质体,是一种特殊的岩土介质类型,有着独特的工程环境特性和工程地质性质。珊瑚礁工程地质研究是现代工程地质学的一个新课题,是近年来为适应珊瑚岛礁工程建设的需求而发展起来的。介绍了珊瑚礁工程地质研究的内容及意义,综述了国内外珊瑚礁工程地质研究的历史现状及其进展,指出应将珊瑚礁体作为工程岩体,进行工程地质环境区带划分及各区带工程地质条件评价;分析礁岩体结构特征和礁体稳定性及其影响因素;分析礁体工程适宜性、地基及其环境与工程活动相互关系。针对珊瑚礁岩土的土力学特点,加强珊瑚礁颗粒破碎机理及其对工程地质性质影响机制的研究;建立能够代表珊瑚礁应力—应变特性的本构关系。     

热带风暴过程中珊瑚礁坪示踪砂运移的现场实验研究

１９９５年１０月在小东海珊瑚礁海岸的礁坪上进行了示踪砂运动的现场实验。本次实验对浪,流以及示踪砂采样作了同步观测。根据所获的实验数据,分析在９５１６号热带风暴天气过程礁坪上示踪砂运移的基本规律。在一级近似下,测定并计算了泥沙在波生流作用下的漂移速度与流速比因子０．００２,混合深度小于２ｃｍ。这一结果与其它已往结果相比明显小得多。     

Biogeochemical contrasts between mid-Cretaceous carbonate platforms and Cenozoic reefs

Carbonate sediments of mid-Cretaceous platforms on Allison and Resolution Guyots, Mid-Pacific Mountains (ODP Leg 143, Sites 865, 866, 867 and 868) and those of upper Oligocene to Pliocene reefs of the Kita-daito-jima Borehole were studied. The mid-Cretaceous platforms abound with abiotic (?) precipitates (ooids) and microbial carbonate grains/sediments (oncoids and ‘algal’ laminites), whereas the Cenozoic reefs consist mainly of coral and non-geniculate coralline algae, major frame-builders, benthic foraminifers and codiacean alga (Halimeda). There exists a remarkable difference in a mode of calcification between the mid-Cretaceous platforms and Cenozoic reefs. The major reef-builders of Cenozoic reefs precipitated carbonates within closed to semiclosed spaces within their bodies. In contrast, the mid-Cretaceous platforms contain abundant grains/sediments formed by chemical (?) precipitations and biotic extracellular calcification. This contrasting feature reflects different modes of biogeochemical cycles between the mid-Cretaceous and Cenozoic. Increased CO₂ (degassed by active volcanism) and resultant high temperature and intensive weathering may have brought high concentration of Ca²⁺ and HCO₃^? into the mid-Cretaceous sea, which enhanced abiotic and extracellular calcification. Inverse processes are true for the Cenozoic.     

广西十万大山盆地下二叠统生物礁古油藏及隐伏礁预测

广西宁明县亭亮下二叠统茅口组生物礁古油藏,为十万大山盆地已暴露破坏的礁古油藏之一。该古油藏的含沥青储层主要分布于礁体的上部和顶部,含沥青礁灰岩厚达９８ｍ以上,礁储层次生溶孔的形成与分布主要受控于深埋有机溶剂作用,同时在空间上还与礁顶部古风化壳和不整合面密切相关,论文深入探讨了礁古油藏形成的主要成岩作用类型及其埋藏一构造发展史,有机质演化史及成岩孔隙演化史三者的配置关系和成藏机理,另据地震和电法资料     

岩鹭在厦门海岸带的分布及其生态考察

岩鹭是我国二级保护鸟类,处于稀有的濒危状态。１９９３年３￣５月,１９９３年９月至１９９４年９月和１９９５年５￣１０月的考察结果。证实岩鹭在厦门的居留时间为１０月上旬至６月上旬。厦门的岩鹭分布于东部海岸,该区域人为干扰和污染少,潮间带底质以砂砾,岩石为主,厦门的岩鹭为灰黑色型,单独活动,种群总数量只有３￣５只,本文根据岩鹭的生态需求、行为习怀和种群数量特点,对岩鹭的保护也进行了讨论。     

环礁沉积体系的过程-产物关系: 勘察式模拟初探

海洋沉积体系的定量模拟可分为仿真和勘察式模拟,后者的目标是建立沉积特征的连续谱、凝练新的科学问题。本文提出一个勘察式模拟的方法论框架,即根据控制方程确定自变量的定义域,进而由模拟计算给出应变量的值域,并结合物质收支平衡原理和“圆台状环礁”几何模型,以此方法预估环礁及其海底阶地物质输运和堆积格局。环礁是珊瑚礁的独特类型,其礁盘区提供了礁体生长和礁外坡、海底阶地堆积的几乎全部物源。结果表明,环礁自身生长受控于生物碎屑生产,而海底阶地的范围和沉积速率不仅决定于离礁悬沙通量,而且受到环礁外水深和海盆环流的制约。悬沙输运和重力流过程形成常态沉降和水下滑坡的交替沉积。此模型所预测的环礁沉积体系高程-面积曲线与南海环礁的实际曲线相对照,可获得环礁演化的机制信息。模拟结果还提示了需进一步研究的科学问题,如环礁生长规模及其控制机制、环礁沉积体系中周期性沉积的时间尺度、环礁外坡由于珊瑚生长自组织机制形成的重力流事件与地震等极端事件的对比和机制识别、环礁群的海底阶地沉积记录多样性、海面变化对环礁演化的影响和沉积记录、环礁人居环境安全等。     

基于大涡模拟与被动示踪物模型的人工鱼礁数值研究

投放人工鱼礁是解决海洋生态环境问题的重要措施之一。通过使用并行大涡模拟模式（the parallelizeda large-eddy simulation model,PALM）及被动示踪物模型模块,研究了不同流速条件（0.1,0.2,0.4和0.6 m/s）下方型人工鱼礁对流场形态、营养盐的抬升作用、和湍流动能收支的影响。研究表明,鱼礁的存在使得其附近垂向速度增大,产生上升流。受到上升流的抬升作用,鱼礁底部的示踪物迅速进入海洋上层,之后遇到鱼礁后方的背涡流,示踪物的抬升受阻,高度逐渐降低。在上升流区域以及背涡流区域的共同影响下,示踪物抬升区域的最大高度与来流流速无关。不同上升流定义对应的上升流区域的高度与来流流速均不相关;上升流区域的最大速度、平均速度与来流流速都成线性增加的关系;然而随着来流流速的增大,不同上升流定义对应的上升流区域面积的变化趋势却完全不同。投放鱼礁后,鱼礁区域底部的混合增强,区域底部的能量被输运至上层。这说明,鱼礁的存在不仅对营养物质具有抬升作用,还能将能量向上输运。     

海洋生物诞生过程、新资源发掘与高值利用

本文以46亿年来地球、海洋及生命的形成与演化为主线,简要回顾了生命体由简单到复杂、从低级向高级、从水生到陆生逐级演化的历史进程,以及重大环境变化事件对生物毁灭性灭绝、生物适应与多样性演化的影响,阐明海洋尤其热带海洋在生命诞生、孕育及庇护等过程中所发挥的不可替代作用。同时,分析了热带海洋生物资源多样性中心形成的重要自然环境因素及可能机制。并针对印太交汇区深海极端环境微生物生态系统、浅海典型的海草/藻床、珊瑚礁、生物多样性和热带渔业资源,论述了热带海洋生物多样性资源的保护、发掘与高值开发利用。     

Source and supply of sediment to a shoreline salient in a fringing reef environment

Reef-associated landforms are coupled to the health of the reef ecosystem which produces the sediment that forms and maintains these landforms. However, this connection can make reef-fronted coastlines sensitive to the impacts of climate change, given that any decline in ecosystem health (e.g. decreasing sediment supply) or changes to physical processes (e.g. sea level rise, increasing wave energy) could drive the sediment budgets of these systems into a net erosive state. Therefore, knowledge of both the sediment sources and transport mechanisms is required to predict the sensitivity of reef-associated landforms to future climate change. Here, we examine the benthic habitat composition, sediment characteristics (composition, texture, and age), and transport mechanisms and pathways to understand the interconnections between coastal morphology and the reef system at Tantabiddi, Ningaloo Reef, Western Australia. Benthic surveys and sediment composition analysis revealed that although live coral accounts for less than 5% of the benthic cover, coral is the dominant sediment constituent (34% on average). Sediment ages (²³⁸U/²³⁰Th) were mostly found to be thousands of years old, suggesting that the primary sediment source is relic reef material (e.g. Holocene reef framework). Sediment transport across the lagoon was quantified through measurements of ripple migration rates, which were found to be shoreward migrating and responsible for feeding the large shoreline salient in the lee of the reef. The derived sediment fluxes were comparable with previously measured rates of sediment production by bioerosion. These results suggest that sediment budgets of systems dependent on old (>10³ years) source materials may be more resilient to climate change as present-day reef health and community composition (i.e. sources of ‘new’ carbonate production) have limited influence on sediment supply. Therefore, the vulnerability of reef-associated landforms in these systems will be dictated by future changes to mechanisms of sediment generation (e.g. bioerosion) and/or physical processes. © 2018 John Wiley & Sons, Ltd.     

Dynamic simulation of tropical coral reef ecosystem being disturbed by multiple situations

In consideration of the rapid degradation of coral reef ecosystems, the establishment of models is helpful to comprehend the degradation mechanism of coral reef ecosystems and predict the development process of coral reef communities. According to the characteristics of complex ecosystem of tropical coral reefs in China, the coral reef functional group is the core level variable; combined with the multiple feedback effects of coral reef functional groups and environmental changes, the study presents a coral reef ecosystem dynamics model with hermatypic corals as the core. Based on the simulation of the assumed initial value and the internal feedback of the system, the results show that in the basic simulation(relative health conditions), the coverage area of live corals and coral reefs generally decreased first and then increased, and increased by 4.67% and 6.38% between2010 and 2050, respectively. Based on the calibration model and the current situation of the studied area, the multi-factor disturbance effects of coral reef communities were simulated and explored by setting up three scenarios involving fishing policy, terrestrial deposition, and inorganic nitrogen emissions. Among them, in the single factor disturbance, the fishing policy exerts the most direct impact on the community decline; and the succession phenomenon is obvious; the terrestrial sedimentation has a faster and more integrated effect on the community decline; the effect of inorganic nitrogen emission on the community decline is relatively slow. In the double/multi-factor disturbance, the superimposed disturbance will aggravate the multi-source feedback effect of the coral reef communities development, accelerate the community decay rate, and make its development trajectory more complicated and diverse. This method provides a scientific and feasible method for simulating the damage of long-term coral reef community and exploring the development law and adaptive management of coral reef ecosystems. In the future, it can be further studied in the ecological restoration process and decisionmaking direction of coral reefs.